1. Field of the Invention
The invention relates to a ball bearing that is lubricated by oil.
2. Description of Related Art
A rolling bearing is used to support a rotary shaft of a rotation portion included in a vehicle, a machine tool, or the like, and a ball bearing is known as the rolling bearing.
FIG. 8 is a sectional view of a double row angular contact ball bearing 99 that supports a rotary shaft 94. The ball bearing 99 includes an outer ring 98, an inner ring 97, balls 96 disposed in double rows, and a cage 95 that retains the balls 96 in each row at intervals in a circumferential direction. The ball bearing 99 is lubricated by oil around the ball bearing 99. The ball bearing 99 is described in, for example, Japanese patent application publication No. 2010-7788.
In the ball bearing 99 shown in FIG. 8, the diameter of an inner peripheral surface 98a of the outer ring 98 increases from one side toward the other side in the axial direction. Therefore, when the inner ring 97 is rotated together with the rotary shaft 94, the oil flows in an area between the outer ring 98 and the inner ring 97 from the one side toward the other side in the axial direction (that is, a pumping action is caused). When the pumping action is caused due to the rotation of the ball bearing 99, the oil outside the bearing flows into the bearing inner area from the one side in the axial direction, and flows out from the other side in the axial direction. In FIG. 8, the flow of the oil is indicated by two-dot chain arrows.
When the oil passes through the bearing inner area, resistance to stirring is caused in the ball bearing 99. Therefore, as the amount of oil passing through the bearing inner area increases, the resistance to stirring increases, and as a result, the running torque of the ball bearing 99 increases. This decreases the rotational performance. The pumping action may be caused in a single row angular contact ball bearing, as well as in a double row angular contact ball bearing. Further, even in the case where the balls do not make angular contact with the inner ring and the outer ring, the pumping action may be caused depending on the shape of an inner peripheral surface of the outer ring, or the shape of an outer peripheral surface of the inner ring, or the pumping action may be caused by the rotation of the cage.
In the ball bearing described in Japanese Patent Application Publication No. 2010-7788, the size of an annular portion positioned on an oil inflow side in the cage is increased to reduce a clearance between the inner ring and the outer ring, and to reduce the inflow of the oil.